Sheet feeder for printing presses

ABSTRACT

The invention relates to a sheet feeding mechanism for printing presses with rotating pregripper. The mechanism provides considerably higher machine speeds. A rotating pregripper is driven by a Maltese cross transmission such that there is a relatively short resting time on a relatively long acceleration angle. The rotating pregripper is equipped with grippers which withdraw under its surface. The pregripper is located under a sheet feeding table having front lays which come from below a throw on aligning or pre-aligning device in covered state. Side lays in covered state are provided on the table along with a sheet displacing mechanism for releasing the side lays. By the arrangement of this mechanism the acceleration and braking times are increased by the square, i.e., quadruple to approximately 200* in order to achieve the desired motion features yet not result in higher forces of acceleration. For the shifting way of the sheets yet not result in higher forces of acceleration. For the shifting way of the sheets the rotating pregripper has means for laterally shifting the same after throwon and until sheet transfer. This last mentioned shifting means has means responsive to the side lays being used so that when lateral alignment of the sheet is not attained before leaving the front lays it is reached before sheet transfer from the rotating pregripper.

United States Patent 1 Schiinemann SHEET FEEDER FOR PRINTING PRESSES [75] Inventor: Hans-Bernhard Bolza Schiinemann,

Wurzburg, Germany [73] Assignee: Schnellpressenfabrik Koenig &

Bauer Aktiengesellschaft, Wurzburg, Germany [22] Filed: Dec. 22, 1971 [21] Appl. No.: 210,897

Primary ExaminerEvon C. Blunk Assistant Examiner-Bruce l-I. Stoner, Jr. Attorney, Agent, or Firm-Jones & Lockwood Feb. 12, 1974 [57 ABSTRACT The invention relates to a sheet feeding mechanism for printing presses with rotating pregripper. The mechanism provides considerably higher machine speeds. A rotating pregripper is driven by a Maltese cross transmission such that there is a relatively short resting time on a relatively long acceleration angle. The rotating pregripper is equipped with grippers which withdraw under its surface. The pregripper is located under a sheet feeding table having front lays which come from below a throw on aligning or prealigning device in covered state. Side'lays in covered state are provided on the table along with a sheet displacing mechanism for releasing the side lays. By the arrangement of this mechanism the acceleration and braking times are increased by the square, i.e., quadruple to appro imately 200 in order to achieve the desired motion features yet not result in higher forces of acceleration. For the shifting way of the sheets yet not result in higher forces of acceleration. For the shifting way of the sheets the rotating pregripper has means for laterally shifting the same after throwon and until sheet transfer. This last mentioned shifting means has means responsive to the side lays being used so that when lateral alignment of the sheet is not attained before leaving the front lays it is reached before sheet transfer from the rotating pregripper.

PATENTEB FEB I 2 I974 SHEET 2 BF 3 Fig. 2

Fly. 3

PAIENTED FEB 1 2 I974 sum a nr 3 SHEET FEEDER FOR PRINTING PRESSES BACKGROUND OF THE INVENTION Sheet feeder devices for printing presses are already known. They consist of a feeding table with stream feeder, front lays operating from above or from below, side lays as well as pregripper, either going back and forth or rotating, which takes the aligned sheets from standstill, accelerates them and passes them on at circumferential speed to the impression cylinder or to a transfer drum.

In most different makes there are pregrippers above or below the feeding table. In case of rotating pregrippers there are some with one, two, three or more gripper systems whereby use is made of pregrippers of usual construction or there is withdrawing under the surface. Some rotating pregrippers work together with sheet displacers or they are subject to special laws of motion in order to temporarily remove the total sheet faster from the feeding table than corresponds to the speed of the impression cylinder. The resting times of the rotating pregrippers are very different and they oscillate from very short to extremely long times. Despite their diversity all of these known sheet feeders have their operating speeds limited and, until now, there is no criterion by which the many known possibilities are to be combined most favorably in a system and which of the many features are possibly not to be combined.

Proposals are made to draw off the first sheet from the side and front lays in order to free these for the following sheet. Through the U.S. Pat. No. 2,892,630 it is known to accelerate the trailing end of the sheet. The US. Pat. No. 2,831,436 shows how the entire sheet is first of all accelerated and then anew retarded and finally delivered at the speed of the press. Grippers which withdraw themselves under the surface are described in the German patent No. 1,212,562.

A sheet adjusting device for sheets in covered state is described in the German patent No. 1,159,967 and shown in its FIG. 5, 6 and 11, 12, 13 and in US. Pat No. 3,001,788.

The German patent No. 653,308 deals with sheet side shifting in order to free the side lay when sheets come in a close sheet stream.

In the US. Pat No. 3,540,723, there is described a Maltese cross having five slotted holes and being provided for driving a folding apparatus.

SUMMARY OF THE INVENTION Therefore the object of the invention is the task of creating sheet feeder which allows considerably higher machine speeds than have been achieved today.

According to the invention the task is solved by a new combination of different features separately already known, but consisting of, as disclosed in the above refered to patents which are herein incorporated by reference in the present application.

a rotating pregripper with short resting time on long throw-on angle, placed under thefeeding table and equipped with grippers which can withdraw under the surface of the pregripper, as well as front lays from below, a sheet aligning device or prealigning device in covered state, and side lays as well as a sheet displacing device setting free the side lays in covered state.

According to the invention this new combination of already known single features has a surprising effect and allows an increase of the capacity to nearly the double of todays most modern printing presses. The great majority of all todays modern machines working with pregrippers going back and forth and whose acceleration forces depend on the acceleration and braking times measured in rotary angles of the impression cylinders.

Typical times are as follows:

50 throw-on time, 20 synchronism, 50 braking time, 60 waiting time, 15 swing-back time, 30 from standstill to close grippers for the 360 cycle. To reach the double capacity, as required, the throw-on and braking times should increase by the square i.e., quadruple to approximately 200 in order to get the same motion features and not result in higher forces of acceleration.

To solve the given task the pregrippers swinging back and forth are to be completely excluded, as they only may reach, even if the times are symetrically divided up I and without any standstill, a throw-on angle and a 90 braking angle per each swing back and forth.

Rotating pregrippers spare the swinging back and can be brought to a maximum of slow-down time, calculating a 36 stand-still time there can be disposed of 162 to accelerate until sheet transfer and 162 to slow down. These are values not applied to any printing machine until now, and which, when mechanically applied, allow the increased efficiency as required. However not only the forces at the pregripper are to be considered but there has to remain enough time to align the sheets on the feeding table.

It is well known that supported by differential or overlay gears as per German patent No. 952,904 practically every desired motion for rotating pregrippers can be produced, however, those gears served to speedily remove the total sheet from the feeding table as per German patent No. 864,399. When the feeding drum is placed under the feeding table, however, the front lays come from above and cannot close earlier than the trailing edge of the sheet that just left the feeding table. Thus the aligning process of the next sheet begins too late. Should the differential gear be used to produce a 162 throw-on angle for the feeding drum, approximately 86 of cylinder turn would be lost, until the feeding drum and sheet would have reached cylinder speed, whereas the cylinder groove is only drawn 60 long. According to this no time at all would remain for adjustment of front and side lays, on the contrary, there would be a deficiency 26. Therefore the front lays should come from below as disclosed, for example, in US. Pat. No. 3,001,788 to make the adjustment possible while the trailing edge of the sheet has not yet left the feeding table. Both of the two above last mentioned German patents neither give a rule for the invented new combination nor do they suggest it.

According to German Auslegeschrift 1,102,766 it is already known to place a stop drum under the feeding table and to use front lays from below. Contrary to the combination according to this invention a long resting time for sheet aligning is explicitely required and also an arrangement of at least three grippers on the feeding drum is required drum so that there is 240 resting time and only during each 60 does the throw-on and braking angle arise.

In spite of the correct placing of the drum and front lays under the feeding table, the German patent 1,102,766 does not contain any hint to a possibly doubled capacity as it was ignored or not appreciated that short resting times are necessary and no long ones, as well as special grippers withdrawing under the surface of the drum and a special equipment at the side lay. Nor does the described gear give any hint of how to reach considerably larger throw-on angles as the usual Maltese crosses only allow throw-on angles up to approximately 60. The originator of the patent ignores or did not appreciate the possibility of the herein invented combination and describes the classic process of sheet feeding with which only the sheet feeder reaches a stop under the front lays so early that the whole time of sheet aligning (here depending on the cylinder groove of the impression cylinder and not on a special equipment of the feeding table) can await a sheet with open grippers. This long waiting time correspondingly shortens the throw-on and braking times of the rotating pregripper so that the high capacities of the herein disclosed and claimed invented combination can not be reached. Only the invented combination solves the task of approximately doubling the capacity of the present systems of sheet aligning and feeding.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is diagrammatically illustrated, by way of example, with reference to the accompanying drawings.

FIG. 1 is a side elevational view of the feeding table, pregripper gear and impression cylinder,

FIG. 2 is a partial top plan view of FIG. 1,

FIG. 3 shows the control geometry of the gear and FIG. 4 shows a time diagram of the invented combination.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 the sheets are aligned in a known manner on a feeding table 1 with front lays 2 and side lays 3 or 3.1 respectively. The front lays 2 come from below. After the aligning at the side lays 3 the sheet is drawn from the side lay 3 by a suction drawing manifold 5 recessed in the topface of table 1 at an always constant amount 4 of about 20 mm so that the following sheet can be aligned undisturbedly at the side lay 3. A rotating pregripper 6 lies under the feeding table 1 and has two gripper systems 7 equipped in a known manner as dip grippers as in German Pat. No. 1,212,562 hereinabove referred to and which can withdraw under the surface of the pregripper 6.

Also reversal or suction grippers are to be used which do not touch an already aligned sheet in released state at the feeding table 1. The grippers 7 pass the sheet to a transfer drum 8 which passes the sheet on to an impression cylinder 9. From tooth wheel 8a on the transfer drum 8 a driving plate 10 is driven through toothed wheels 10a thereon. Driving plate 10 has three driving rolls ll spaced thereon at 120 and the driving plate 10 is driven at a transmission rate of 1 3. The driving rolls dive one after the other into five switch slotted holes 12.1 ofa Maltese cross 12. The Maltese cross 12 makes a switch step of 360 divided by 5 equals to 72, per single-tour or single turn revolution of the transfer drum 8. The switch step is geared by toothed wheels 13, 14 at a ratio of 2.5 l to the pregripper 6. With each switch step of the Maltese cross 12 the pregripper 6 is turned through 180.

FIG. 3 shows the known cooperation of Maltese cross 12 and driving plate 10. As there are 3 driving rolls 11 the distance therebetween amounts to 120. The fivepart Maltese cross 12 makes switch steps of 72 possible. Therefore half a switch step is 36 so that, when diving right-angularly, half the driving angle can only amount to 54. There is still a remaining angle of 6 which each driving roll has to pass on both sides, a total angle of 12, before the acceleration of the Maltese cross starts. The diameter of the Maltese cross 12 is effectively larger by these 1 6 curve pieces as indicated at 12.2, and the slotted holes extend outwardly in a circular arc shape correspondingly to the radius which the driving rolls 11 form. At the 1 6 driving roll motion in the circular arc segment of the slotted holes of the Maltese cross a perfect, right-angular blocking of the Maltese cross is realized. As the driving plate 10 is geared down at a ratio of 1 3 to the single turn of transfer drum 8 respectively to the impression cylinder 9, the resting time of the pregripper 6 is 3 X 6 (6 entrance and 6 exit) (a total angle of 12) 3 X 12 36 which is enough to close the gripper 7. In FIG. 3 the acceleration angle a and braking angle b of 54 each are shown. The throw-on angle and braking angle each are 3 X 54 162 of the single-tour shaft turn as compared to 60 or less with Maltese transmissions known at present. In view of this advantage or feature a very considerable speed increase of the printing machine can take place.

FIG. 4 shows a time diagram of the herein invented combination for a diameter of impression cylinder amounting to 300 mm which corresponds to 942 mm circumference and a maximum sheet size of 820 mm. Corresponding with this the cylinder groove only amounts to 46 or 122 mm. A sheet aligning time of 60 at the front lay and 90 at the side lay is taken as a basis. The feeding drum starts its motion at 0 of impression cylinder turn. After 75 the front lay closes the feeding drum starts so slowly that it then moves only 40 mm. After 90 the second sheet touches the front lay and has 60 (VM) slowing time until 150. Then the side lay starts and draws until 240, i.e., 90 (ZM) long. At a machine speed of 8,000 sheets/hr. momentary drawing times of approximately 32 are normal; treble drawing times are not reached so that considering the side lay, too, there are no objections to double the machine speeds. As the trailing edge of the running sheet does not set free either the line of front lays or the line of the side lay, the front lays have to come from below so that the running trailing edge is able to cover the lays still without disturbing the aligning of the following sheets. As the line of the side lay is covered as well when the following sheet is due to be drawn, every sheet is drawn back from the side lay at a constant amount of 20 mm after drawing is effected so that the side lay will be immediately free for the following sheet. This placing back of the sheet is made in a known manner by a suction manifold 5 at the feeding table. Therefore there can be disposed of (SL) from 240 to 330 impression cylinder turn. The pregrippers come to rest at the feeding table at 334 to 360 and close in the range of 300 to 360. During this space the running sheet has not yet left the feeding table which is quite new to do, the feeding drum too has to operate from below and seize the next sheet while the trailing edge of the sheet has not yet left the feeding table. As one may recognize a gap between trailing edge and next sheet develops not earlier than after 405, i.e., 45 after the throw-on of the pregripper.

Thus the new feeding system accomplishes the given task. It allows a maximum throw-on angle of the feeder. As shown, in the time diagram, however, every process is executed covered by the previous sheet, these large throw-on angles are only possible when the front lays and the sheet feeder operate on the sheets in covered state, i.e., both have to be placed under the feeding table.

Furthermore the side lay must be free as same has to also operate in a covered state. This may be done in known manner according to the German Patent 653,308 and U.S. Pat. No. 3,001,788, both heretofore referred to by lateral shifting of the pregripper after throw-on until sheet transfer whereby longer aligning times arise, e.g., VM 90 and ZM 150 as shown in the lower part of FIG. 4. There are known means for shifting the rotating pregripper which bar known means responsive to a side lay means being used whereby when lateral alignment of the sheet is not reached before leaving the front lays it is reached before sheet transfer from said rotating pregripper. If desired a known belt deceleration on the feeding table may be additionally used. The doubling of the machine capacity is possible only when being able to produce several times larger acceleration angles of the sheet feeder and several times longer aligning times at the front lays and side lays simultaneously. The invented system solves this task for the first time.

What is claimed is:

1. A sheet feeder for a printing machine including an impression cylinder on a single revolution shaft, said sheet feeder comprising a feed table; a rotating pregripper having a cylindrical surface and positioned under the sheet feeding end of said feed table, said pregripper having sheet grippers mounted therein for withdrawal beneath said surface, said grippers being positioned in two rows spaced 180 apart along said surface; front lay means mounted adjacently below the sheet feeding end of the feed table and adapted to move from therebelow for sheet aligning and feeding to said pregripper and being adapted for front aligning of the sheets in covered state; said feeding table having side lay means having sheet displacing means setting free the side lays in covered state;

and drive means for driving said pregripper through successive stopped, acceleration, constant speed, and deceleration periods in each of rotation thereof, said drive means comprising: (1) a Maltese cross having five equally spaced, radially extending drive slots, (2) a rotating driving plate having three circumferentially equally spaced driving rolls thereon for driving cooperation with said slots, (3) drive gear means for driving the pregripper from said Maltese cross, said drive gear means driving said pregripper from said Maltese cross, said drive gear means driving said pregripper at a ratio of 2.5 to l, and (4) driving means for rotating said driving plate and its driving rolls at a geared down ratio equivalent to one turn of said driving plate to three turns of said single revolution shaft; said drive slots of the Maltese cross having at their entrance ends oppositely disposed walls shaped as oppositely extending circular arc curves wherein said Maltese cross drive is temporarily blocked between two of said driving rolls when positioned in the entrance ends of two adjacent respective slots.

2. A sheet feeder for a printing machine according to claim 1 including a sheet transfer drum on a single revolution shaft rotating at the same speed as said impression cylinder on its single revolution shaft for transferring sheets from said rotating pregripper to said impression cylinder, said driving means for rotating said driving plate and its driving rolls being a tooth wheel on said single revolution shaft of said sheet transfer drum driving a tooth wheel of said driving plate at a geared down ratio of one turn to three turns of said single revolution shaft of the transfer drum.

3. A sheet feeder according to claim 2 including means for laterally shifting of said rotating pregripper after acceleration and until sheet transfer, said last named means having means responsive to said side lay means being used whereby when lateral alignment of the sheet is not reached before leaving the front lay means it is reached before sheet transfer from said rotating pregripper.

4. A sheet feeder according to claim 1 including means for laterally shifting of said'rotating pregripper after acceleration and until sheet transfer, said last named means having means responsive to said side lay means being used whereby when lateral alignment of the sheet is not reached before leaving the front lay means it is reached before sheet transfer from said rotating pregripper. 

1. A sheet feeder for a printing machine including an impression cylinder on a single revolution shaft, said sheet feeder comprising a feed table; a rotating pregripper having a cylindrical surface and positioned under the sheet feeding end of said feed table, said pregripper having sheet grippers mounted therein for withdrawal beneath said surface, said grippers being positioned in two rows spaced 180* apart along said surface; front lay means mounted adjacently below the sheet feeding end of the feed table and adapted to move from therebelow for sheet aligning and feeding to said pregripper and being adapted for front aligning of the sheets in covered state; said feeding table having side lay means having sheet displacing means setting free the side lays in covered state; and drive means for driving said pregripper through successive stopped, acceleration, constant speed, and deceleration periods in each 180* of rotation thereof, said drive means comprising: (1) a Maltese cross having five equally spaced, radially extending drive slots, (2) a rotating driving plate having three circumferentially equally spaced driving rolls thereon for driving cooperation with said slots, (3) drive gear means for driving the pregripper from said Maltese cross, said drive gear means driving said pregripper from said Maltese cross, said drive gear means driving said pregripper at a ratio of 2.5 to 1, and (4) driving means for rotating said driving plate and its driving rolls at a geared down ratio equivalent to one turn of said driving plate to three turns of said single revolution shaft; said drive slots of the Maltese cross having at their entrance ends oppositely disposed walls shaped as oppositely extending circular arc curves wherein said Maltese cross drive is temporarily blocked between two of said driving rolls when positioned in the entrance ends Of two adjacent respective slots.
 2. A sheet feeder for a printing machine according to claim 1 including a sheet transfer drum on a single revolution shaft rotating at the same speed as said impression cylinder on its single revolution shaft for transferring sheets from said rotating pregripper to said impression cylinder, said driving means for rotating said driving plate and its driving rolls being a tooth wheel on said single revolution shaft of said sheet transfer drum driving a tooth wheel of said driving plate at a geared down ratio of one turn to three turns of said single revolution shaft of the transfer drum.
 3. A sheet feeder according to claim 2 including means for laterally shifting of said rotating pregripper after acceleration and until sheet transfer, said last named means having means responsive to said side lay means being used whereby when lateral alignment of the sheet is not reached before leaving the front lay means it is reached before sheet transfer from said rotating pregripper.
 4. A sheet feeder according to claim 1 including means for laterally shifting of said rotating pregripper after acceleration and until sheet transfer, said last named means having means responsive to said side lay means being used whereby when lateral alignment of the sheet is not reached before leaving the front lay means it is reached before sheet transfer from said rotating pregripper. 